Control method and control system for a hydraulic retarder

Abstract

A control method and control system of a hydraulic retarder, comprising: obtaining a slope of a downhill section ahead of a vehicle; judging whether an absolute value of the slope of the downhill section ahead of the vehicle is greater than an absolute value of a slope without brake force intervention; if greater, predicting a required brake force when the vehicle travels on the slope of the downhill section ahead and an oil amount required to reach the brake force; predicting a corresponding oil filling time according to the oil amount; predicting a distance between the vehicle and a starting point of the downhill section ahead when the hydraulic retarder starts to fill oil according to the oil filling time; when the actual distance between the vehicle and the starting point of the downhill section ahead is equal to the predicted distance, controlling the hydraulic retarder to start to fill oil; and when the vehicle travels to the starting point of the downhill section ahead, controlling the hydraulic retarder to start to brake. The hydraulic retarder is started to fill oil before reaching the downhill position, and the hydraulic retarder is started to brake when reaching the downhill position, so as to reduce brake pad wear and tear and reduce vehicle operation cost loss.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle control, in particular to a control method and control system of a hydraulic retarder. BACKGROUND

[0002] The wear of brake pads is very serious when heavy trucks brake, and physical friction type braking has the problem of thermal failure. The retarder is another type of braking system on heavy trucks, especially the hydraulic retarder, which has the advantage that the braking heat can be conducted in time, and the structure is simple, safe and convenient. However, the hydraulic retarder needs to have the process of filling brake fluid into the retarder to generate braking force, and has a hysteresis effect in response time, so it is not suitable for real-time or emergency braking.

[0003] At present, the hydraulic retarder is generally opened manually by the driver, and is mostly used on long downhills to reduce the wear of the friction type braking system, but most drivers still have the habit of only stepping on the brake, and it is difficult to ensure that the hydraulic retarder can be correctly opened by relying on the subjective operation of the driver. In order to realize automatic control of the hydraulic retarder, the Chinese patent with the patent number CN201510321728 and the patent name "Control system and control method of hydraulic retarder" combines the opening and closing of the hydraulic retarder with the depth of the brake pedal, but this simple combination control method is easy to trigger false, which affects the economy and maneuverability. SUMMARY

[0004] The main purpose of the present application is to provide a control method and control system of a hydraulic retarder, which is based on the prediction and advance control of the front road information to start the hydraulic retarder at the appropriate time, so as to reduce the wear of brake pads and reduce the operating cost loss of the vehicle.

[0005] The present application adopts the following technical solutions:

[0006] On the one hand, the present application provides a control method of a hydraulic retarder, which comprises:

[0007] obtaining the slope of the downhill section in front of the vehicle;

[0008] determining whether the absolute value of the slope of the downhill section in front of the vehicle is greater than the absolute value of the slope without the intervention of braking force;

[0009] if greater, predicting the braking force required by the vehicle when driving on the downhill section in front of the vehicle at a stable speed, and the amount of oil required to reach the braking force;

[0010] predicting the corresponding oil filling time according to the amount of oil;

[0011] predicting the distance between the vehicle and the starting point of the downhill section in front of the vehicle when the hydraulic retarder is opened and filled with oil according to the oil filling time;

[0012] When the actual distance of the vehicle to the start point of the front downward slope section is equal to the predicted distance, the hydraulic retarder is controlled to start oil filling;

[0013] When the vehicle travels to the start point of the front downward slope section, the hydraulic retarder is controlled to start braking.

[0014] Preferably, after the step of controlling the hydraulic retarder to start braking when the vehicle travels to the start point of the front downward slope section, the method further comprises:

[0015] When the vehicle ends traveling on the front downward slope section, the hydraulic retarder ends braking.

[0016] Preferably, the calculation formula of the slope without brake force intervention is as follows:

[0017]

[0018] wherein θ min represents the slope without brake force intervention, μ represents the road surface friction coefficient, C d represents the air density, H represents the vehicle frontal area, V a represents the vehicle frontal wind speed, m represents the mass of the vehicle and the load, and g represents the gravitational acceleration.

[0019] Preferably, the required brake force of the vehicle when traveling on the front downward slope section at the predicted stable vehicle speed, and the required oil amount to reach the brake force, specifically comprises:

[0020] The required brake force T r of the vehicle when traveling on the front downward slope section at the predicted stable vehicle speed, the calculation formula is as follows:

[0021] T r = mg(θ-θ min )

[0022] wherein m represents the mass of the vehicle and the load, g represents the gravitational acceleration, θ represents the slope of the front downward slope section, and θ min represents the slope without brake force intervention.

[0023] According to the required brake force, the required oil amount Q to reach the brake force is calculated as follows:

[0024]

[0025] wherein v1 represents the flow speed of the oil at the rotor impeller inlet of the hydraulic retarder; v3 represents the flow speed of the oil at the rotor impeller inlet; R1 represents the radius of the oil inlet of the rotor impeller; R3 represents the radius of the oil outlet of the rotor impeller; and ρ represents the oil density.

[0026] Preferably, the required braking force of the vehicle when driving on the slope of the downhill road section in front and the required oil volume to achieve the braking force at the predicted stable vehicle speed are specifically as follows:

[0027] Calibrating the required braking force of the vehicle when driving on the slope of the downhill road section in front and the corresponding oil volume at different vehicle speeds;

[0028] Obtaining the current driving speed of the vehicle, and based on the calibrated data, obtaining the required braking force T of the vehicle when driving on the slope of the downhill road section in front r , and the required oil volume Q to achieve the braking force; the calibrated data includes the calibrated vehicle speed, the required braking force and the corresponding oil volume data.

[0029] Preferably, the calibrated vehicle speed, the required braking force and the corresponding oil volume data are stored in the form of a data table, a curve or a curve.

[0030] Preferably, according to the oil volume, the corresponding oil filling time is predicted, and the calculation formula is as follows:

[0031]

[0032] Wherein, t represents the oil filling time; Q represents the oil volume; C represents the flow coefficient; A1 represents the flow cross-sectional area of the oil filling pipeline; V1 represents the average speed of oil filling.

[0033] Preferably, according to the oil filling time, the distance between the vehicle and the starting point of the downhill road section in front when the hydraulic retarder is started to fill oil is predicted, as follows:

[0034] Offset = Vt

[0035] Wherein, Offset represents the predicted distance, t represents the oil filling time; V represents the stable driving speed of the vehicle.

[0036] On the other hand, the control system of the application comprises a front road information acquisition module, a brake controller and a hydraulic retarder;

[0037] The front road information acquisition module is used to acquire the front road information of the vehicle and send the front road information to the brake controller; the front road information includes the slope of the downhill road section in front of the vehicle and the distance between the vehicle and the starting point of the downhill road section in front;

[0038] The brake controller is used to realize the control method of the hydraulic retarder as claimed in any one of claims 1 to 8;

[0039] The hydraulic retarder receives the control of the brake controller and performs corresponding actions; the actions include starting oil filling, ending oil filling, starting braking or ending braking.

[0040] Preferably, the front road information acquisition module is realized by an electronic horizon.

[0041] Compared with the prior art, the present application has the following advantages:

[0042] The present application is a kind of hydraulic retarder control method and control system, suitable for vehicle speed stable cruise state, based on front road information for prediction and early control, at the right time to start hydraulic retarder, to solve the existing control in the error trigger and mitigation hydraulic retarder response delay problem; At the same time, due to the start of hydraulic retarder brake, so as to reduce the time of using brake when the terrain changes, reduce the brake pad wear, reduce the cost of vehicle operation loss, economy is good. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The flowchart of the method of the present application is shown in the figure.

[0044] Figure 2 The structure diagram of the system of the present application is shown in the figure. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present application clearer, the following will combine the figures to make further detailed description of the embodiments of the present application.

[0046] The method execution subject of the present embodiment is a vehicle brake controller, which can install the execution program and / or database program of the method of the present embodiment, and the specific application of the present application is not limited.

[0047] It should be noted that the step identifiers involved in the claims and the specification of the present application are only for the purpose of making the file clearer, and the order of the steps can be adjusted accordingly according to the needs in specific implementation.

[0048] Referring to Figure 1 The control method of the hydraulic retarder provided by the present embodiment comprises:

[0049] S101, acquiring the slope of the downhill section in front of the vehicle;

[0050] S102, judging whether the absolute value of the slope of the downhill section in front of the vehicle is greater than the absolute value of the no-braking-force-intervention slope;

[0051] S103, if the absolute value of the slope of the downhill section in front of the vehicle is greater than the absolute value of the no-braking-force-intervention slope, predicting the braking force required by the vehicle when driving on the downhill section in front of the vehicle at a stable speed, and the oil quantity required to achieve the required braking force;

[0052] S104, predicting the corresponding oil filling time according to the required oil quantity;

[0053] S105, predicting the distance between the vehicle position and the start point of the front slope section when the hydraulic retarder starts to charge oil according to the oil charging time;

[0054] S106, controlling the hydraulic retarder to start to charge oil when the actual distance between the vehicle position and the start point of the front slope section is equal to the predicted distance;

[0055] S107, controlling the hydraulic retarder to start to brake when the vehicle reaches the start point of the front slope section.

[0056] After step S107, the hydraulic retarder stops to brake when the vehicle finishes the slope section; or after step S107, the hydraulic retarder stops to brake when the slope of the slope section changes and the absolute value of the slope is less than the absolute value of the slope without brake force intervention.

[0057] In the embodiment, the calculation formula of the slope without brake force intervention is as follows:

[0058]

[0059] wherein, θ min represents the slope without brake force intervention; μ represents the road surface friction coefficient; C d represents the air density; H represents the vehicle windward area; V a represents the vehicle windward speed, which is approximately equal to the current vehicle speed V in ideal case; m represents the mass of the vehicle and the load; g represents the gravity acceleration.

[0060] Specifically, according to the force balance equation of automobile dynamics, the current resultant force of the automobile is equal to the difference between the forward force provided by the engine and the resistance of the automobile to the outside world. The calculation formula of the current resultant force of the automobile is as follows:

[0061] F a = F-F rot -F slope -F acc -F win

[0062] wherein, F a represents the current resultant force of the automobile, F rot represents the friction resistance between the vehicle tire and the ground, F slope represents the gravity resistance of the slope, F acc represents the resistance to overcome the moment of inertia caused by the acceleration of the vehicle, F win represents the wind resistance of the vehicle.

[0063] Further, the external resistance to the vehicle can be obtained by the following calculation formulas respectively:

[0064] F rot = mgμ

[0065] F slope = mgθ

[0066] F acc = mδa

[0067]

[0068] wherein θ represents the slope of the downhill road section in front of the vehicle, a represents the acceleration of the vehicle, and δ represents the moment of inertia.

[0069] Since the vehicle is in a cruising state, the acceleration a of the vehicle is 0, and thus F a and F acc are both equal to 0.

[0070] Since when the slope is θ = θ min the braking force does not need to be involved, at this time when the engine output is 0, it can just maintain the current cruising speed, and thus F is also equal to 0.

[0071] Then the above formula F a = F - F rot - F slope - F acc - F win can be converted to:

[0072] F slope = -F rot - F win

[0073] that is:

[0074]

[0075] It can be obtained that:

[0076]

[0077] In an embodiment, the braking force required by the vehicle when driving on the downhill road section with a slope in front at a stable vehicle speed, and the oil amount required to reach the braking force, are predicted, and specifically include:

[0078] The braking force T r required by the vehicle when driving on the downhill road section with a slope in front at a stable vehicle speed is predicted as follows:

[0079] T r = mg(θ - θ min )

[0080] Obtaining the oil volume Q required to reach the braking force, as follows:

[0081]

[0082] Wherein, v1 represents the flow velocity of the oil at the rotor impeller inlet of the hydraulic retarder, v3 represents the flow velocity of the oil at the rotor impeller inlet, since the rotor of the hydraulic retarder is fixed on the vehicle drive shaft and rotates with the drive shaft, the flow velocity of the oil can be approximately equal to the rotational speed of the vehicle drive shaft; R1 represents the radius at the oil inlet of the rotor impeller, R3 represents the radius at the oil outlet of the rotor impeller, R1 and R3 are constants; ρ represents the oil density, and ρ is a constant.

[0083] In another embodiment, the braking force required by the vehicle when driving on a slope of a downhill road section ahead at a stable vehicle speed, and the oil volume required to reach the braking force, can also be:

[0084] Calibrating the braking force required by the vehicle when driving on a slope of a downhill road section ahead at different vehicle speeds, and the corresponding oil volume;

[0085] Obtaining the current vehicle speed, and based on the calibrated data, obtaining the braking force T r required by the vehicle when driving on a slope of a downhill road section ahead, and the oil volume Q required to reach the braking force; the calibrated data includes calibrated vehicle speed, required braking force, and corresponding oil volume data.

[0086] The calibrated vehicle speed, required braking force, and corresponding oil volume data are stored in the form of a data table, a MAP curve diagram, or a curve.

[0087] Specifically, a calibration method can be used to calibrate a series of braking torques T r required to reach a series of different braking torques T r at a series of different vehicle speeds V, and the oil volume Q required for each braking torque.

[0088] For example, when V = 50 km / h, the corresponding relationship between the braking force T r and the oil volume Q is as shown in Table 1 (N max represents the maximum braking force that can be reached at this vehicle speed, and Q max represents the maximum oil volume that can be filled at this vehicle speed):

[0089] Table 1

[0090] T r (N)]]> Q(L) 1 0.7 1.5 1.3 2 2.2 …… …… [0000001] N[0000002] max [0000003] ​ Q max ]]>

[0091] In addition, a plurality of calibration tables at different vehicle speeds can be integrated together to generate a three-dimensional calibration MAP diagram, and the three axes are T rV and Q, in the three-dimensional calibration MAP, through the value of V axis and T r axis, find out the value of Q.

[0092] Further, according to the oil quantity, the corresponding oil filling time is predicted, as follows:

[0093]

[0094] Wherein, t represents the oil filling time; Q represents the oil quantity; C represents the flow coefficient; A1 represents the flow cross-sectional area of the oil filling pipeline; V1 represents the average speed of oil filling.

[0095] Further, according to the oil filling time, the distance between the vehicle position when the hydraulic retarder is started to fill oil and the starting point of the front downhill section is predicted, as follows:

[0096] Offset = Vt

[0097] Wherein, Offset represents the predicted distance, t represents the oil filling time; V represents the vehicle speed when the vehicle is stably running.

[0098] In the embodiment, when the brake controller determines that the vehicle reaches the position of the distance downhill Offset, the vehicle speed is kept stable and cruise, and the hydraulic retarder is started to fill oil, so that when the position of the downhill is reached, the engine does not output torque, the hydraulic retarder plays a braking role, and the vehicle can maintain the original cruise speed at a constant speed without the engine output force, so that the fuel consumption is saved, the brake pad is avoided to be worn, and good economy is achieved.

[0099] Referring to Figure 2 , in another aspect, the application provides a control system, comprising a front road information acquisition module 201, a brake controller 202 and a hydraulic retarder 203;

[0100] The front road information acquisition module 201 is used to acquire the front road information of the vehicle, and send the front road information to the brake controller 202; the front road information includes the slope of the downhill section in front of the vehicle and the distance between the current position of the vehicle and the starting point of the downhill section in front of the vehicle;

[0101] The brake controller 202 is used to realize the hydraulic retarder control method provided by the application;

[0102] The hydraulic retarder 203 accepts the control of the brake controller 202 and performs corresponding actions; the actions include starting to fill oil, ending to fill oil, starting to brake or ending to brake.

[0103] In the embodiment, the front road information acquisition module acquires the front road information of the vehicle through an electronic horizon. Of course, other devices can also be used as long as the function of the front road information acquisition module can be realized, and the application does not make specific limitations.

[0104] The above is only a specific embodiment of the application, but the design concept of the application is not limited thereto, and any non-essential modification of the application using this concept shall be deemed to be an infringement of the protection scope of the application.

Claims

1. A control method of a hydraulic retarder, characterized by, The method comprises: acquiring the slope of a downhill road section ahead of the vehicle; judging whether the absolute value of the slope of the downhill road section ahead of the vehicle is greater than the absolute value of a slope without intervention of braking force; if greater, predicting the braking force required by the vehicle when driving on the downhill road section ahead at a stable vehicle speed, and the oil volume required to reach the braking force; predicting the corresponding oil filling time according to the oil volume; predicting the distance between the vehicle and the starting point of the downhill road section ahead when the hydraulic retarder starts oil filling according to the oil filling time; controlling the hydraulic retarder to start oil filling when the actual distance between the vehicle and the starting point of the downhill road section ahead is equal to the predicted distance; controlling the hydraulic retarder to start braking when the vehicle drives to the starting point of the downhill road section ahead; the prediction of the braking force required by the vehicle when driving on the downhill road section ahead at a stable vehicle speed, and the oil volume required to reach the braking force, specifically comprises: The required braking force T of the vehicle when running on a downhill road section at a steady vehicle speed Vst is predicted r The calculation formula is as follows: T r = mg(θ - θ min ) where m represents the mass of the vehicle and the load, g represents the acceleration of gravity, θ represents the gradient of the downhill road section in front of the vehicle, and θ min represents the gradient without the intervention of the braking force. calculating the oil volume Q required to reach the braking force according to the required braking force as follows: wherein v1 represents the flow velocity of oil at the rotor impeller inlet of the hydraulic retarder; v3 represents the flow velocity of oil at the rotor impeller inlet; R1 represents the radius of the rotor impeller oil inlet; R3 represents the radius of the rotor impeller oil outlet; and p represents the oil density.

2. The control method of the hydraulic retarder according to claim 1, characterized by, after the controlling of the hydraulic retarder to start braking when the vehicle drives to the starting point of the downhill road section ahead, the method further comprises: controlling the hydraulic retarder to end braking when the vehicle ends driving on the downhill road section ahead.

3. The control method of the hydraulic retarder according to claim 1, characterized by, the calculation formula of the slope without intervention of braking force is as follows: where θ min represents the slope without the intervention of braking force, μ represents the road surface friction coefficient, C d represents the air density, H represents the vehicle frontal area, V a represents the vehicle frontal wind speed, m represents the mass of the vehicle and the load, and g represents the acceleration of gravity.

4. The control method of the hydraulic retarder according to claim 1, characterized by, the prediction of the braking force required by the vehicle when driving on the downhill road section ahead at a stable vehicle speed, and the oil volume required to reach the braking force, specifically comprises: calibrating the required braking force and the corresponding oil volume of the vehicle when driving on the downhill road section ahead at different vehicle speeds; acquire the current speed of the vehicle, and acquire the required braking force T of the vehicle when driving on a downhill road section in front based on calibrated data r and the required oil amount Q to reach the braking force; the calibrated data includes calibrated speed, required braking force, and corresponding oil amount data.

5. The control method of a hydraulic retarder according to claim 4, characterized in that, the calibrated vehicle speed, required braking force and corresponding oil volume data are stored in the form of a data table, a curve diagram or a curve.

6. The control method of a hydraulic retarder according to claim 1, characterized by, the calculation formula of the prediction of the corresponding oil filling time according to the oil volume is as follows: wherein t represents the oil filling time; Q represents the oil volume; C represents the flow coefficient; A1 represents the flow cross-sectional area of the oil filling pipeline; and V1 represents the average oil filling speed.

7. The control method of a hydraulic retarder according to claim 1, characterized by, the calculation formula of the prediction of the distance between the vehicle and the starting point of the downhill road section ahead when the hydraulic retarder starts oil filling according to the oil filling time is as follows: Offset = Vt wherein Offset represents the predicted distance, t represents the oil filling time; and V represents the stable driving speed of the vehicle.

8. A control system characterized by, The method comprises: a front road information acquisition module, a brake controller and a hydraulic retarder; the front road information acquisition module is configured to acquire front road information of the vehicle and send the front road information to the brake controller; the front road information comprises the slope of a downhill road section ahead of the vehicle and the distance between the vehicle and the starting point of the downhill road section ahead; the brake controller is configured to implement the control method of the hydraulic retarder according to any one of claims 1 to 7; 9. The control system of claim 8, wherein, the hydraulic retarder is controlled by the brake controller and performs corresponding actions; the actions comprise starting oil filling, ending oil filling, starting braking or ending braking. the front road information acquisition module is implemented by an electronic horizon.

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